Colorado DUID figures

Chart from “The Legalization of Marijuana in Colorado: The Impact, Volume 3 Preview 2015”

Colorado traffic safety officials say the impact in the state of marijuana-impaired drivers is not yet clear from a recent report, Chhun Sun wrote for The Gazette.

As this blog has reported, the Colorado State Patrol has said:

Of the 4,546 citations issued for DUI/DUID driving in 2015, 347 were issued for driving when marijuana was the only infraction of the law, whereas in 665 of the citations, more than marijuana was involved.

Study Sample Inconclusive

Trooper Josh Lewis said the sample size in the study was too small to provide enough information on which to base any conclusions about whether or not the legalization of recreational marijuana in Colorado has made the roads less safe:

We can’t say one way or another what we anticipate in the coming years, but we’re going to continue our efforts.

Focus on Drunk Driving

Colorado Department of Transportation spokesman Sam Cole told Sun that although pot-impaired driving can be as dangerous as drunk driving, the department is focusing on drunk driving since it is a larger issue. However, Cole said, “Unfortunately, many marijuana users admit to driving high and are unconcerned with the impairment it causes.”

In 2014, more than a third of the Colorado’s 488 traffic deaths were related to alcohol consumption. By comparison, of the 684 drivers involved in fatal accidents, 84 tested positive for marijuana.

Dangers of Driving Stoned

Cole pointed out that marijuana-impaired driving existed in the state long before recreational use was legalized. The difference, he said, is that Colorado now has the funds to boost law enforcement training and conduct public outreach on the dangers and legal consequences of driving stoned.

According to CDOT’s Marijuana and Driving page, a driver who has used marijuana cannot judge his or her own level of impairment. Any amount of pot puts a driver at risk of driving impaired.

Under Colorado law, a driver with 5 nanograms or more of THC (the psychoactive component of marijuana) per milliliter of blood can be prosecuted for DUI. But officers are legally allowed to base arrests on their observations of impairment, regardless of the THC level.

Stoned Driving Behavior Studied

In an article appearing on TheWeedBlog, Paul Armentano, deputy director of  the National Organization for the Reform of Marijuana Laws (NORML), points to a study published in the Journal of Applied Toxicology which found that marijuana-affected driving ability is “significantly” different than drunk driving behavior. The study, conducted by the National Institute on Drug Abuse and the University of Iowa, was based on driving simulator data. Study subjects used the driving simulator after consuming either vaporized cannabis, alcohol, or a placebo.

The researchers found that test subjects who had consumed cannabis displayed compensatory behavior while using the driving simulator, like a slower mean speed, and an extra following distance. Those findings correspond with other driving studies. Such compensatory driving behavior contrasts with the driving of the alcohol-impaired, who show higher-risk behavior such as driving at a greater than normal speed.

Armentano went on to say that according to the findings of a recently published literature review of crash culpability studies,

[A]cute cannabis intoxication is related to a statistically significant risk increase of low to moderate magnitude [odds ratio between 1.2 and 1.4].

By contrast, a 2015 case-control study by the U.S. National Highway Traffic Safety Administration found that driving with legal blood-alcohol levels is associated with an increased car crash risk of 1 to 3.93.